AbstractI will discuss cosmic inflation with a single light field in the presence of other, very massive fields. The inflationary trajectories are generically not straight. Whenever there is a turn in the trajectory, very heavy fields (with masses much larger than the Hubble scale) can leave a distinctive imprint on the spectrum of primordial perturbations. The main effect is a reduction in the speed of sound of the adiabatic perturbations, which leads to features in the power spectrum correlated with an enhancement of non-gaussianity.